A new projection-based approach derived from the Radon transform for detecting and estimating 3-D locations of unresolved targets in a time-sequential set of infrared imageries is presented. Since the signal-to-noise ration per pixel is very low (a dim target) and target tracks which span over many image frames. Since the 2-D multiple representations along arbitary orientations utilizing the 3-D Radon transform, our projection-based transform method enables us to analyze the 3-D problem in terms of its 2-D projections. Our method not only alleviates the great computatioonal expense of processing entire set of images as a whole, but the results reveal that the proposed strategy produces a robust detection and estimation of 3-D target trajectories event at low SNRs.